The present invention relates to an electromagnetic actuator and a valve-open-close mechanism used mainly in an automotive internal combustion engine.
Conventional valve-open-close mechanism actuated by electromagnetic actuators are disclosed e.g. in Japanese patent publication 11-93629. Explaining with reference to FIG. 1, which shows one embodiment of this invention, an electromagnetic actuator 4 includes a pair of electromagnets 6, 7 each made up of a stator 5 and a coil 18 that are opposed to each other with a gap S therebetween. An armature 3 is disposed in the gap S so as to be reciprocable between two electrotromagnets 6, 7. A first stem 15 for transmitting the movement of the armature 3 from one electromagnet 6 toward the other electromagnet 7 to a valve 9 for an internal combustion engine is provided on one side of the armature 3, namely, at the side where there is the electromagnet 7.
Also, the electromagnetic actuator 4 is housed in a housing 8 fixed to an internal combustion engine body 19; the tip of the first stem 15 of the electromagnetic actuator is brought into abutment with the tip of the valve 9 so that when the armature 3 is moved from the electromagnet 6 toward the electromagnet 7, the first stem 15 opens the valve 9 by pushing it; in order to impart a biasing force to the valve for a valve-closing operation, a retainer 13 is provided on the valve 9, and a first return spring 2 is mounted between the retainer 13 and the internal combustion engine body 19; a second stem 14 is provided on the armature 3 on the side opposite to the side coupled to the first stem 15; and a retainer 13xe2x80x2 is provided on the second stem 14, and a second return spring 1 for imparting a biasing force in the direction in which the second stem 14 pushes the armature 3 is mounted between the retainer 13xe2x80x2 and the housing 8.
In this valve-open-close mechanism, the weights of the directly driven parts during actuation have a direct influence on the driving power consumption of the electromagnetic actuator 4 as an inertia weight. Such parts slide during actuation and the friction during sliding motion of the parts has a direct influence on the power consumption. Since the driving power is normally supplied from the on-board battery, an increase in the power consumption is not preferable.
To reduce the power consumption, not only the lessening of weights of the parts but reduction of the sliding friction are necessary.
An object of this invention is to reduce the sliding friction of the parts forming the valve-open- close mechanism.
According to the present invention, there is provided an electromagnetic actuator comprising a pair of electromagnets each made up of a stator and a coil, a movable element comprising an armature and a first stem for transmitting the force that acts on the armature to an external load, characterized in that a coating film is formed on a surface or an end face of the first stem.
A valve-open-close mechanism can be formed by use of such an electromagnetic actuator.
According to this invention, by forming the coating film, it is possible to reduce the sliding friction, reduce the driving power consumption for the electromagnetic actuator and reduce the fuel consumption if it is used in an automobile.
According to the present invention, the electromagnetic actuator comprises a pair of electromagnets each made up of a stator and a coil opposed to each other with a gap therebetween; an armature disposed in the gap so as to be reciprocable between the pair of electromagnets by driving the electromagnets; and a first stem for transmitting to external the movement of the armature from one electromagnet toward the other electromagnet, the first stem being provided at a moving side of the armature; the electromagnetic actuator being housed in a housing fixedly mounted to an internal combustion engine body; the armature being moved from the one electromagnet toward the other electromagnet, so that the first stem opens the valve by pushing the valve; the electromagnetic actuator further comprising a first retainer provided on the valve for imparting a biasing force to the valve for a valve-closing operation, and a first return spring mounted between the first retainer and the internal combustion engine body; a second stem provided at a surface of the armature on the side not coupled to the first stem; and a second retainer provided on the second stem, and a second return spring mounted between the second retainer and the housing for imparting a biasing force to urge the armature, a coating film being formed on at least one of the front face or end face of the stem portion of the valve, end faces of the first return spring or second return spring, spring bearing end faces of the retainers, surface or end face of the second stem, and the surface of the armature.